The present invention relates in general to the art of nailing, and, more in particular, to the art of automatic nailing tools.
Nails for years have been driven by hand-held hammers. In comparatively recent times nailing guns have become available. The guns are usually pneumatically powered, extracting energy from compressed air to drive nails at the command of a gun's operator. The guns have a body housing the passages, valving and pistons used in converting the pneumatic energy into the kinetic energy of the driver. A driver head of the gun has a firing chamber that receives individual nails and orients nails into the path of the driver. A magazine feeds nails to the chamber.
The nails for automatic nailing guns have come either prepackaged or loose. Prepackaged nails are oriented with their axes in a plane, their heads overlapping, their shafts parallel, and their shafts held together by parallel plastic bands. A spring-loaded follower urges the banded nails towards the chamber of the gun. With the driving of each nail, a new nail advances into the chamber for subsequent driving. Prepackaged nails are more expensive than loose nails because of the requirement for packaging. Some prepackaged nails have a portion of their heads sheared off to avoid double driving, the head shearing is an additional fabrication expense. The packaging comes apart upon the driving of the nails and can make the work place slippery and hazardous. Spring-fed followers tend to buckle the nails that they are urging against, limiting the number of nails in a package of nails.
Attempts have been made to overcome the disadvantages of prepackaged nail guns. One such gun is described in U.S. Pat. No. 4,136,810. That patent describes a loose nailing gun having a magazine that orients the nails in echelon fashion for feed into the firing chamber of a gun. Feed is by gravity. A dog in the firing chamber holds a nail there and retracts in response to a force applied to it through the nail head by the driver.
A loose nail gun is also described in U.S. Pat. No. 3,504,840 to O. A. Wandel et al. The Wandel device has a magazine that has a worm that advances nails serially into the firing chamber of the gun. It maintains nail orientation and displacement by the restraint of the lands of the worm at the cost of complication, expense and weight.
A third type of a loose nail gun is described in U.S. Pat. No. 3,491,932 to Novak. The Novak device utilizes a nail arrest of a toothed plate; each tooth has a ramp that permits nail advance and the retraction of the plate from the path of nails and a steep shoulder that prevents nail kickback in a direction opposed to nail advance. This nail arrest necessitates a wide magazine and is attendant with considerable mechanisms for its working. It is not responsive to free nails when the gun disengages from the workpiece in order to assure orderly advance of the nails.
A fourth device is described in U.S. Pat. No. 3,820,705 to Beals. Beals shows a gravity-fed magazine that feeds nails into the driving chamber of the nail gun and holds them there through a spring-loaded detent. The weight of the nails is aided by a weight trailing the nails. There is no provision for nail arrest or for preventing a trailing nail from underriding the head of a nail in front of it.